Allen Afield: Easy for fishermen, fish to get hooked on Light Cahills

A large pool on the Kennebec River between Solon and North Anson produces magnificent Light Cahill hatches each June, a large, cream mayfly tied on a size 12 or 14 hook. I lean toward the size 14 choice.

1. The pool mostly holds brown trout. When they surface to sip dead-drift mayflies, I sneak within close casting distance, taking care to avoid making tiny wavelets that spread across the surface and spook trout.

2. During hatches where insects float at exactly the same speed as the current, my plan entails dropping the fly above the rise ring, so the fly drifts back over the brown’s lie without drag — no matter how slight. If the insect’s speed differs even minutely from the flow, it turns ultra-wary fish off cold.

Subtle drag can be difficult to ascertain unless the caster looks at a simple indicator such as a bit of foam, surface debris such as a leaf or blade of grass or anything beside the imitation fly. The fly and the free-floating item must be moving at exactly the same speed.

Drag begins when shifts in the surface film pull on the leader or line and “drag” the fly unnaturally across the surface. To beat this problem, veteran fly rodders change casting angles by moving a step or two left or right or maybe tie on a longer tippet and cast so it lands loosely on the surface. The latter allows the fly to float with the current until the leader straightens out and begins pulling on the fly.

A feature of the pool makes the fish spooky. The surface has shifting vagaries in the current that create myriad drags, and to complicate matters, the pool averages about six feet deep. Trout often lie near bottom and must rise up 51/2 feet to take the fly, a long ascension that gives them ample time to eyeball the prize. If anything is wrong, these fish have time to spot it.

I have named it “Light Cahill Pool,” and every brown and occasional brookie that sips my fly there fills me with pride. It’s a tough pool, one of those places that fills our heads with images for winter daydreams.

When I say Light Cahills, I’m talking about more than one species and even genera in Maine. About the time the bulk of the June Light Cahills have hatched, another fun mayfly starts hatching in earnest.

This next mayfly has a few colloquial names, and popular ones include “Leadwing” or “White-gloved Howdy,” because the bug has lead-colored wings, and two white front legs and four dark brown back ones. Serious Maine fly rodders may call it “Isony,” a short version of the Latin name “Isonychia bicolor.” Bicolor refers to the two leg colors.

This swimming nymphs in the Isonychia genus have a fascinating emergence routine. Before shucking the larval case, larvae swim to objects sticking above the water — the dry tops of river rocks, shore rocks, tree trunks lying into the water or the sides of bridge abutments.

In these spots away from the maws of hungry fish, they crawl on top before bursting from the nymphal case to become duns. Because of that, fish don’t always rise to the duns, but rather they concentrate on nymphs, moving in the current. This rule has exceptions for sure.

These bugs often match the size of imitations tied on 10 or 12, 2x long hooks, depending on the water. A Zug Bug, a common, popular nymph pattern, imitates the natural Isonychia larvae well. Naturally, nymph imitations constructed just for imitating this mayfly also work.

Fly rodders in the know cast quartering across and downstream, let the fly swing in a tight arc like a horizontal pendulum, and then inch the fly back against the current like a swimming nymph.

It helps to stand in a river current and try to spot an Isony nymph swimming below the surface, which shows the caster the precise movement to duplicate.

In the right light, this isn’t an impossible task, but sometimes it is difficult to see nymphs below the surface. Yes, no one ever said that fly fishing doesn’t require exceptional observation skills.

When trout forage on Isonychia nymphs, folks with a Zug Bug or Isony imitation cast down and quartering across, and retrieve the fly upstream an inch or two at a time. This can produce dynamite evenings.

Micro blue-winged olives hatch all summer and offer good sport, but in June and early July, Light Cahill and Isonychia dry flies and nymphs, as well as Hex nymphs and dries can keep the good times rolling.

I’ve written about Hexes, probably one too many times here, but for day-in and day-out excitement, Light Cahills and Isony nymphs in June and early July really create great fun with rather consistent, predictable hatches.

Ken Allen, of Belgrade Lakes, a writer, editor and photographer, may be reached at:

Here at MaineToday Media we value our readers and are committed to growing our community by encouraging you to add to the discussion.

To ensure conscientious dialogue we have implemented a strict no-bullying policy. To participate, you must follow our Terms of Use. Click here to flag and report a comment that violates our terms of use.